At some point we started getting “_59f.getMonth is not a function” JavaScript issue each time we render forms with the dijit.form.DateTextBox. Further investigation showed that the issue happens just in FireFox and not in Chromium. So I’ve configured unobfuscated Dojo and Spring JS files and started debugging comparing things in two browsers.

Pretty soon it became vivid that in Chrome we get Date object for parsing while in Firefox we got String object. After a bit of debugging I’ve seen that localization data used for initialization of date formats was really different.